40 research outputs found
Compaction dynamics in ductile granular media
Ductile compaction is common in many natural systems, but the temporal
evolution of such systems is rarely studied. We observe surprising oscillations
in the weight measured at the bottom of a self-compacting ensemble of ductile
grains. The oscillations develop during the first ten hours of the experiment,
and usually persist through the length of an experiment (one week). The weight
oscillations are connected to the grain--wall contacts, and are directly
correlated with the observed strain evolution and the dynamics of grain--wall
contacts during the compaction. Here, we present the experimental results and
characteristic time constants of the system, and discuss possible reasons for
the measured weight oscillations.Comment: 11 pages, 14 figure
Discrete space-time geometry and skeleton conception of particle dynamics
It is shown that properties of a discrete space-time geometry distinguish
from properties of the Riemannian space-time geometry. The discrete geometry is
a physical geometry, which is described completely by the world function. The
discrete geometry is nonaxiomatizable and multivariant. The equivalence
relation is intransitive in the discrete geometry. The particles are described
by world chains (broken lines with finite length of links), because in the
discrete space-time geometry there are no infinitesimal lengths. Motion of
particles is stochastic, and statistical description of them leads to the
Schr\"{o}dinger equation, if the elementary length of the discrete geometry
depends on the quantum constant in a proper way.Comment: 22 pages, 0 figure
Validation of Deep Convolutional Generative Adversarial Networks for High Energy Physics Calorimeter Simulations
In particle physics the simulation of particle transport through detectors
requires an enormous amount of computational resources, utilizing more than 50%
of the resources of the CERN Worldwide Large Hadron Collider Grid. This
challenge has motivated the investigation of different, faster approaches for
replacing the standard Monte Carlo simulations. Deep Learning Generative
Adversarial Networks are among the most promising alternatives. Previous
studies showed that they achieve the necessary level of accuracy while
decreasing the simulation time by orders of magnitudes. In this paper we
present a newly developed neural network architecture which reproduces a
three-dimensional problem employing 2D convolutional layers and we compare its
performance with an earlier architecture consisting of 3D convolutional layers.
The performance evaluation relies on direct comparison to Monte Carlo
simulations, in terms of different physics quantities usually employed to
quantify the detector response. We prove that our new neural network
architecture reaches a higher level of accuracy with respect to the 3D
convolutional GAN while reducing the necessary computational resources.
Calorimeters are among the most expensive detectors in terms of simulation
time. Therefore we focus our study on an electromagnetic calorimeter prototype
with a regular highly granular geometry, as an example of future calorimeters.Comment: AAAI-MLPS 2021 Spring Symposium at Stanford Universit
Thermo-mechanical homogenization of composite materials
Postprint (published version
Gambini-Pullin Electrodynamics as a scenario for Cherenkov radiation in QED vacuum
We examine the electromagnetic radiation produced by a moving charge in the
QED vacuum that behaves as a dispersive medium characterized by a geometrical
structure (discreteness/granularity) that emerges from loop quantum gravity. It
is shown that the radiation is driven by the refractive vacuum the charged
particle travels through reproducing the profile of the Cherenkov effect.Comment: 6 page
Generalizing to new calorimeter geometries with Geometry-Aware Autoregressive Models (GAAMs) for fast calorimeter simulation
Generation of simulated detector response to collision products is crucial to
data analysis in particle physics, but computationally very expensive. One
subdetector, the calorimeter, dominates the computational time due to the high
granularity of its cells and complexity of the interaction. Generative models
can provide more rapid sample production, but currently require significant
effort to optimize performance for specific detector geometries, often
requiring many networks to describe the varying cell sizes and arrangements,
which do not generalize to other geometries. We develop a {\it geometry-aware}
autoregressive model, which learns how the calorimeter response varies with
geometry, and is capable of generating simulated responses to unseen geometries
without additional training. The geometry-aware model outperforms a baseline,
unaware model by 50\% in metrics such as the Wasserstein distance between
generated and true distributions of key quantities which summarize the
simulated response. A single geometry-aware model could replace the hundreds of
generative models currently designed for calorimeter simulation by physicists
analyzing data collected at the Large Hadron Collider. For the study of future
detectors, such a foundational model will be a crucial tool, dramatically
reducing the large upfront investment usually needed to develop generative
calorimeter models